Intermediate-mass black holes associated with cloud collisions
Abstract
Ultraluminous X-ray sources (ULXs) are non-nuclear point X-ray sources with X-ray luminosities intermediate between those of stellar mass black holes and supermassive black holes. Recently, theorists have proposed viable mechanisms of creating the new class of intermediatemass black holes (100-1000 Msun ) that must be necessary if accretion onto these ULXs is to obey the Eddington limit. ULXs are often associated with colliding systems. The spiral galaxy M99 is a good example: M99 has been strongly affected by tidal interactions and recent close encounters, responsible for an asymmetric spiral pattern and a high star-formation rate. My XMM-Newton study shows that at the outskirts of the galaxy, away from the main starforming regions, there is a ULX with an X-ray luminosity ∼ 1 × 1040 erg/s. This source is close to the location where a massive HI cloud appears to be falling onto the M99 disk at a relative speed >100 km/s. I speculate that fast cloud collisions may trigger large-scale dynamical collapses of molecular cloud cores, leading to the formation of very massive (>200 Msun ) stellar progenitors; I argue that such stars may later collapse into intermediate-mass black holes (∼100 Msun ) if their metal abundance is sufficiently low. Thus, I suggest that there is a direct link between collisional environments and intermediate-mass black hole formation.
- Publication:
-
37th COSPAR Scientific Assembly
- Pub Date:
- 2008
- Bibcode:
- 2008cosp...37.3486W